eighteen minutes to tell you what happened over the past six million yearswe all have come from a long way here in africa and converged in this region of africa which is a place where ninety percent of our evolutionary process took placeand i say that not because i am african but it's in africa that you find the earliest evidence for human ancestorsall right i'm a paleoanthropologist and my job is to define man 's place in nature and explore what makes us human and today i will use selam the earliest child ever discovered to tell you a story of all of usin december of two thousand in an area called dikika it's in the northeastern part of ethiopia and selam means peace in many ethiopian languages we use that name to celebrate peace in the region and in the planeti did some digging because that's what we do to know about my host you don't just jump into an invitation and i learned that the first technology appeared in the form of stone tools two point six million years agofirst entertainment comes evidence from flutes that are thirty five thousand years old and evidence for first design comes seventy five thousand years old beads andyou can do the same with your genes and track them back in time and then the analysis of living humans and chimpanzees teaches us today that we diverged sometime around seven million years agoand that these two species share over ninety eight percent of the same genetic material i think knowing this is a very useful context within which we can think of our ancestryhowever then the analysis informs us only about the beginning and the end telling us nothing about what happened in the middle so for us paleoanthropologistsour job is to find the hard evidence the fossil evidence to fill in this gap and see the different stages of development because it's only when you do that that you can talk aboutit's only when you do that you can talk about how we looked like and how we behaved at different times and how those likes and looks and behaviors changed through timethat then gives you an access to explore the biological mechanisms and forces that are responsible for this gradual change that made us what we are todaybut finding the hard evidence is a very complicated endeavor it's a systematic and scientific approach which takes you to places that are remote hot hostile and often with noof the locals and using just shovels and picks i made my way i was the first person to actually drive a car to the spotand you find nothing for years and years when i go to places like this which are paleontological sites it's like going to a game park an extinct game park butwhat you find are not the human remains such as selam and lucy on a day to day basis you find elephants rhinos monkeys pigs et ceterabut you could ask how could these large mammals live in this desert environment of course they cannot but i'm telling you already thatthe environment and the carrying capacity of this region was drastically different from what we have today a very important environmental lesson could be learned from thisanyway once we made it there then it's a game park as i said an extinct game park and our ancestors lived in that game park but were just the minorities they were not as successful and as widespreadas the homo sapiens that we are to tell you just an example an anecdote about their rarity i was going to this place every year and would do field work hereand the assistants of course helped me do the surveys they would find a bone and tell me here is what you're looking for i would say no that's an elephant again another one that 's a monkey that 's a pig et cetera soone of my assistants who never went to school said to me listen zeray you either don't know what you're looking for or you're looking in the wrong placeit was then after such hard work and many frustrating years that we found selam and you see the face here covered by sandstoneand here is actually the spinalcolumn and the whole torso encased in a sandstone block because she was buried by a riverwhat you have here seems to be nothing but contains an incredibleamount of scientific information that helps us explore what makes us humanthis is the earliest and most complete juvenile human ancestor ever found in the history of paleoanthropology an amazing piece of our long long history there were these three people and me and i am taking thehow would you feel if you were me you have something extraordinary in your hand but you are in the middle of nowhere the feeling i had was a deep andquiet happiness and excitement of course accompanied by a huge sense of responsibility of making sure everything is safehere is a close up of the fossil after five years of cleaning preparation and description which was very long and i had to expose the bones from the sandstone block i just showed you in the previous slideit took five years in a way this was like the second birth for the child after three point three million years but the labor was very longand here is full scale it's a tiny bone and in the middle is the minister of ethiopian tourism who came to visit the national museum of ethiopiai was working there and you see me worried and trying to protect my child because you don't leave anyone with this kind of child even a ministerso then once you've done that the next stage is to know what it isthen it was possible to compare we were able to tell that she belonged to the human family tree because the legs the foot and some featuresthe skull with a comparably aged chimpanzee and little george bush here you see that you have vertical foreheadand you see that in humans because of the development of the pre frontal cortex it's called you don't see that in chimpanzees andyou don't see this very projecting canine so she belongs to our family tree but within that of course you do detailed analysis and we know now thatshe belongs to the lucy species known as australopithecus afarensis the next exciting question is girl or boy and how old was she when she diedyou can determine the sex of the individual based on the size of the teeth how you know in primates there is this phenomenon called sexual dimorphism which simply means males are larger than females and males have larger teeth than the femalesbut to do that you need the permanent dentition which you don't see here because what you have here are the baby teeth but using the ct scanning technology which is normally used for medical purposesyou can go deep into the mouth and come up with this beautiful image showing you both the baby teeth here and the still growing adult teeth hereso when you measure those teeth it was clear that she started out to be a girl with very small canine teeth and to know how old she was when she died what you do is you doand you say how much time would be required to form this amount of teeth and the answer was three so thisdied when she was about three three point three million years ago so with all that information the big question is what do we actuallywhat does she tell us to answer this question we can phrase another question what do we actually know about our ancestors we want to know how they looked like how they behaved how they walked around and how theylived and grew up and among the answers that you can get from this skeleton are included firstthis skeleton documents for the first time how infants looked over three million years ago and secondthat she walked upright but had some adaptation for tree climbing and more interesting however is the brain in this child was still growingat age three if you have a still growing brain it's a human behavior in chimps by age three the brain is formed over ninety percentbut that care means also you learn you spend more time with your parents and that's very characteristic of humans and it's called childhood which is this extendeddependence of human children on their family or parents sothe still growing brain in this individual tells us that childhood which requires an incrediblesocial organization a very complex social organization emerged over three million years ago so by being at the cusp of our evolutionary historybut not everything was human and i will give you a very exciting example this is called the hyoid bone it's a bone which is right here it supports your tongue from behindyour voice box it determines the type of voice you produce it was not known in the fossil record and we have it in this skeletonwhen we did the analysis of this bone it was clear that it looked very chimp like chimpanzee like soif you were there three point three million years ago to hear when this girl was crying out for her mother she would have sounded more like a chimpanzee than a human maybe you're wondering so you see thisfeature human feature ape feature what does that tell us you know that is very exciting for us because it demonstrates that things were changing slowly and progressively and that evolution is in the makingto summarize the significance of this fossil we can say the following up to now the knowledge that we had about our ancestors came essentially from adult individualsbecause the fossils the baby fossils were missing they don't preserve well as you know so theknowledge that we had about our ancestors on how they looked like how they behaved was kind of biased toward the adultsimagine somebody coming from mars and his job is to report on the type of people occupying our planet earth and you hide all the babies the childrenand he goes back and reports can you imagine how much biased his report would be that's what somehow we were doing so far in the absence of the fossil children so i think the new fossil fixes this problemso i think the most important question at the end is what do we actually learn from specimens like this and from our past in generalof course in addition to extracting this huge amount of scientific information as to what makes us human you know the many human ancestorsthat have existed over the past six million years and there are more than ten they did not have the knowledge the technology and sophistications that we homo sapiens have todayif this species ancient species would travel in time and see us today they would very much be very proud of their legacynow the question is we homo sapiens today are in a position to decide about the future of our planet possibly moreso the question is are we up to the challenge and can we really do better than these primitive small brained ancestorsamong the most pressing challenges that our species is faced with today are the chronicproblems of africa needless to list them here and there are more competent people to talk about this stillin my opinion we have two choices one is to continue to see a poor ill crying africa carrying guns that depends on other peopleorto promote an africa which is confidentpeaceful independent but cognizant of its huge problems andgreat values at the same time i am for the second option and i'm sure many of you areand the key is to promote a positive african attitude towards africabecause we africans concentrate i am from ethiopia by the way we concentrate too much on how we are seen fromor from outside i think it's important to promote in a more positive way on how we see ourselves that's what i call african positive african attitude so生词表: